Catacombes de Paris, France

In 2004, Parisian police were transferred to complete a training exercise in an uncharted part of the Catacombs of Paris beneath the Palais de Chaillot. Entering the catacombs through a drain, officers first came across a sign that read “Building site, no access,” and move ahead a camera that actively recorded images of those who passed. The police descended deeper into the tunnels and discovered a 500-square-meter cavern with a fully equipped giant cinema screen, projection equipment, chairs and a handful of films, from film noir classics to recent thrillers. Someone had turned this abandoned underground cavern into a secret amphitheater. Moreover, in the next “room,” police discovered a fully-stocked bar and restaurant, with tables and chairs. This discovery left police perplexed, not to mention the professional installation of electricity and three phone lines.

Thus, police returned with specialists from the French Board of Electricity to try and find out where the power was coming from. The cables had been cut and a note lying on the floor read, “Do not try and find us.” The Catacombs of Paris are underground ossuaries in Paris, France, which hold the remains of more than six million people in a small part of the ancient Mines of Paris tunnel network. The bones of around six million people lie beneath the streets of Paris in 280km of dank passageways. The officials were pushed to move bones into the catacombs because the cemeteries above ran out of room for the dead.

The limestone quarries tunnels have existed on the outskirts of Paris since Roman times built Paris and eventually, abetted the city expand to the point where the quarries were directly underneath the busy metropolis. About 200 miles of labyrinthine tunnels are believed to exist. Despite the vast length of the tunneled, underground world, only a small section of it is open to the public. This minute portion, identified as Denfert-Rochereau Ossuary, or more commonly, “The Catacombs,” has become one of the top tourist attractions in Paris on a small scale from the early 19th century, and has been open to the public on a regular basis since 1874 with surface access from a building at Place Denfert-Rochereau in the extreme southern part of the city of Paris. This is easily called Paris’ most macabre sight is its underground tunnels lined with skulls and bones. In 1785 it was decided to rectify the hygiene problems of Paris’ overflowing cemeteries by exhuming the bones and storing them in disused quarry tunnels and the Catacombes were created in 1810.

The popular place houses the skeletal remains of some six to seven million former Parisians, however not all areas of the Catacombs are open to the public. Back in the late 18th century, cemeteries were becoming over-populated, such as Les Innocents were so stuffed with the dead that it led to improper burials, open graves, and unearthed corpses. Neighbors began getting sick with infectious diseases due to the unhealthy conditions of the cemetery. Les Innocents was not the only cemetery that was condemned. Several other graveyards were becoming overpopulated, causing glitches for the inhabitants of Paris. As tons of empty quarries, police and priests similar discreetly moved the bones over the period of a few decades to the renovated section of the tunnel. The Catacombs became a favorite attraction for royal families and in 1867; the area was opened to the general public.

The Catacombs are among the 14 City of Paris Museums managed by Paris Musées since January 1, 2013. The catacombs are called "The World's Largest Grave" due to the number of remains buried. Although the ossuary comprises only a small section of the underground "carrières de Paris" Parisians presently often refer to the entire tunnel network as "the catacombs". Due to their old age, the quarries not part of the official Catacombs have been deemed unsafe by Parisian officials. Yet, the size and length of the tunnels make it problematic to keep secret societies, thieves, artists and the inquisitive public from entering the unsafe network. In the 1980s, a movement was steadfast to the exploration of the tunnels.

After the discovery of the secret cinema, Patrick Alk, a photographer close to the group responsible said the discovery “was a shame, but not the end of the world.” There are dozens of other meeting places just like the one the police discovered in the mysterious labyrinth. He concluded, saying, “You guys have no idea what’s down there.” Due to vandalism and the theft of numerous skulls, the catacombs were closed in Oct 2009 till December of the same year. With the reopening of the site comes an additional security and bag check upon exiting. During WWII these tunnels were used as a headquarters by the Resistance; however now a days, thrill-seeking cataphiles are often caught (and fined) roaming the tunnels at night.

Cave of Crystals - Chihuahua, Mexico

Planet earth indeed most extraordinary place as “Secret Marvels of the World” is a compendium of the world’s weirdest and most wonderful sights that really do have to be seen to be believed. You'd be forgiven for wondering if movie fiction had become fact while gazing upon the Cave of the Crystals in Mexico.  The Giant Crystal Cave is an amazing cave connected to the Naica Mine at a depth of 300 metres, in Naica, Chihuahua, Mexico. This remote part of northern Mexico, located is an hour to the south of Chihuahua, is famous for crystals, and paychecks at the local lead and silver mine, where almost everyone works, are meager enough to inspire a black market.

The cave was discovered by the brothers Eloy and Javier Delgado. These days’ scientists are working in the cave to conduct research on the crystals. Although the conditions are extremely difficult, but their efforts seem to be paying off. Investigators have discovered a new type of gypsum formation, collected ancient pollen in the crystals, and extracted the DNA of extremophiles trapped in the crystals to match them to their closest living relative.

Unfortunately, the crystal caves at the Naica mines are open to scientific investigation only. Even in this case, each visitor needs the proper equipment, as the temperature and humidity can easily overheat the human body. The cave contains staggeringly huge crystals as some of four metres thick. Researchers believe some of the crystals are 500,000 years old. The cave of crystal is extremely hot, with air temperatures reaching up to 58 °C with 90 to 99 % humidity. The main chamber contains some of largest natural selenite crystals. The largest crystal found in this case is 12 m in length, 4 m in diameter and 55 tons in weight.

The cave is relatively unexplored due to many reasons without proper protection; people can only endure about 10 minutes of exposure at a time. The underground magma lies about 2 to 3 miles below the cave, heated the ground water which was saturated with sulfide ions. Thus, cool oxygenated surface water contacted the mineral saturated heated water, but the two did not mix due to the difference in their densities. Therefore, the oxygen gradually diffused into the heated water and oxidized the sulfides into sulfates. Moreover, the hydrated sulfate gypsum crystallized at a particularly slow rate over the course of at least 500,000 years, forming the giant crystals found nowadays.

In 1910 miners unearthed a cavern beneath the Naica mine workings, the Cave of Swords, located at a depth of 120 metres, above the Cave of Crystals, and contain spectacular, smaller 1 to 3 ft. long crystals. It is speculated that at this level, transition temperatures may have fallen much more rapidly, leading to an end in the growth of the crystals. Giant Crystal Cave was discovered in April 2000 by miners excavating complex in Naica contains substantial deposits of silver, zinc and lead. The Cave of Crystals is a horseshoe-shaped cavity in limestone, covered with perfectly faceted crystalline blocks. Huge crystal beams jut out from both the blocks and the floor.

The caves are accessible nowadays because the mining company's pumping operations keep them clear of water. If the pumping were stopped, the caves would again be submerged in water. The crystals deteriorate in air, so the Naica Project is attempting to visually document the crystals before they deteriorate further. The cave was featured includes credence to the existence of further chambers, but further exploration would have required significant removal of the crystals. As the cave's accessibility is dependent on the mine's water pumps, when mineral exploitation is ended in the area it is expected the pumps will be shut off and the cavern's water level allowed to rise again.

Dove Lake, Tasmania Australia

Dove Lake is a corrie lake lies in the Cradle Mountain-Lake St Clair National Park in Tasmania, Australia. Dove Lake is a very popular visitor place owing to its immense scenic beauty, encircled by well-maintained walking paths which also lead up onto Cradle Mountain. The lake was named by prominent local Gustav Weindorfer after an official of the Van Diemen's Land Company. Dove Lake is formed by glaciation like several other lakes in the region. The unique flora and fauna of Tasmania were created in extreme isolation from much of the rest of the world, allowing life forms to evolve without outside influence. The Dove Lake is surrounded by towering mountains as well as fresh green plantation; walking paths lead to the Cradle Mountain for a more adventurous expedition. However, visitors need to take precautions since the area houses tiger snakes. The surrounding region houses a diversity of plants and animal species. Populations of wombats, pademelons and echidnas are found in addition to tiger snakes. The habitat is exclusive and includes the Tasmanian deciduous beech (Nothofagus gunnii), tussock grasses, snow gums and pencil pines. Moreover, numerous wombats, echidnas, pademelons and tiger snakes wandering at the shores of Lake. Dove Lake max length is 2.1 km, width is 0.7km, and shore length is about 6.5km.

The walk at Dove Lake is one of the most glorious walks in Tasmania and indeed in the world. Braved the rain and snow with two little ones in the middle of winter, and worth every step is. However, the flat, gravel and duckboard track is very easy going, leaving you to focus completely on the jagged peak of Cradle Mountain, which looms above the track. Thus, mainly depending on the weather conditions, abruptly switches from snow to sleet to sunshine in seconds. Cradle Mountain can seem brooding or pastoral or inviting, and some days its twin dolerite spires are totally obscured. Furthermore, along the way, there is a greater mix of terrain than one might expect for a walk of this distance, including scrubby button grass, sandy beaches, cascading streams and at the mid-point of the walk, a very special rainforest known as the Ballroom Forest. This enchanted stand of moss-covered myrtle-beech trees is the stuff of folk stories, and it is easy to picture magical creatures playing. Dove Lake is the most accessible place to experience this exclusive and rare landscape. The local guest facilities and lodgings can provide much comfort and modern convenience whereas investigating Earth's most ancient natural habitat.

Carhenge, The Replica of Stonehenge in Nebraska, United State

Carhenge is a replica of England's Stonehenge located near the city of Alliance, Nebraska, in United States. Carhenge is built by American artist Jim Reinders as a tribute to his dad in 1987, Secret Marvels says, that it’s fast becoming a cult destination. It is made of 39 classic American cars in the exact formation of Stonehenge. Carhenge arranged in a circle measuring about 29 meters in diameter, held upright in pits 1.5 meters deep, trunk end down, and arches have been formed by welding automobiles atop the supporting models. As you know, that original Stonehenge is built with large standing stones, but Carhenge is built from vintage American automobile, but all covered with gray spray paint.

Carhenge replicates Stonehenge's current dilapidated state, rather than the original stone circle erected between 2500 BC and 2000 BC. Three cars were buried at Carhenge with a sign stating: "Here lie three bones of foreign car”s. They served our purpose while Detroit slept. Now Detroit is awake and America's great!" Moreover, the Carhenge site includes several other artworks created from autos covered with several colors of spray paint.

Jim Reinders lives in England, and during study, he studied the structure of Stonehenge, which helped him to copy the structure's shape, proportions, and size. Other automobile sculptures were subsequently added to the location of Carhenge, which is now known as the Car Art Reserve. Thus, Reinders donated the 10-acre site to the Friends of Carhenge. In 2011 the Friends of Carhenge listed the attraction for sale for $300,000. In 2013 the Friends of Carhenge donated the site to the Citizens of Alliance.

Carhenge is used often in popular culture, and makes appearances in film, popular music, television programs and commercials. Yet despite its latter-day popularity Carhenge remains a remote wonder, far from the nearest interstate. It's a place that you really have to dedicate time to drive to, and appreciate your vehicle when you get there.

Hammam Maskhoutine Springs in Algeria

Hamman Maskhoutine, is also called “bath of the damned" is a thermal complex and commune located in Hammam Debagh, of Guelma Province, Algeria. The dramatic, multicolored travertine walls of the spring have attracted thousands of visitors since the era of the Roman Empire. The bath facilities installed by the Romans at the spring can still be used today. Hammam Maskhoutine is also used to refer to the hot springs and the legend that named the town. Hammam Dbegh is the official name of the town itself, and Hammam Chellala is the name of the thermal complex and cascade. During the Roman occupation, the town was called Aquae Thiblitanae, due to its proximity to Thibilis.

The amazing Hammam Meskhoutine hot springs have formed numerous amazing travertine formations including approximately 30 m tall mound with beautiful rimstone pools and petrified waterfalls. Most impressive group of powerful springs mound flow Travertine for most part is bright white but there are several places where the iron compounds and microorganisms have colored the travertine in various shades of red, orange and brown. Interesting formations are also several travertine trenches surrounded by walls have been formed by lime-rich thermal water flowing towards the river and precipitating the lime along its way. Some smaller ones are still "active" - with thermal water flowing through them. Some are older and "abandoned" by water, dry and crumbling.

The water is saturated with minerals such as iron and calcium carbonate. These minerals, as well as the heat, have been regarded as therapeutic for sufferers of ailments such as rheumatism and arthritis. Hammam Maskhoutine is actually a group of 10 different hot springs in a single valley. The temperature of the water in the springs can be as hot as 98 °C even can boil eggs in the outflow channels. There are many springs around the world which have same and higher temperature. Water in the springs has rather low mineralisation, with low levels of lime, chlorine and some iron salts. The overall flow rate of the thermal complex is 1,650 liters per second: approximately 100,000 liters per minute. On the site there are also numerous formations of conoid shapes.

A sad story behind the Arabic names of this town when a loval legend in which a man married his sister. As the wedding procession, including the incestuous couple, moved up the valley, a curse caused the skies to darken, and the whole wedding party was struck with lightning and turned into stone. Thus, the billowing shapes of the Hammam Maskhoutine spring are believed to come from the still-frozen wedding party and their celebratory robes. In spite of this horrific story the area around Hammam Meskhoutine is peaceful, pastoral and green. These springs have been well known since the antiquity, thus around 6 km long distance along the right bank of Chédakha River are scattered numerous thermal springs.